Fluid flow control valves are utilized for on/off control or throttling the flow of fluid. Many such flow control valves utilizes a rotating ball control member contacting a ball seal. Such flow control devices are characterized as ball valves which can provide high fluid flow handling capacity for gases, steam, liquid and the fluid with high viscosity, and provide high flow capacity for many different applications in various process industries.
In view of the varied applications of such ball control valves, the ball seal must have wide range of temperature resistance and chemical resistance, as well as hydrolysis resistance (i.e., resistance to the long-term effects of hot water and steam). In addition, it is desired that a ball seal for such flow control valves has sufficient hardness and creep deformation, while also having a low coefficient of friction and exhibiting low air permeability, for reliable sealing without leakage.
When the valve ball is not installed correctly, the fluid in the valve body will occur leakage issue. Otherwise, when the fluid pressure within the valve apparatus is too large, the installation between the elements is not in correctly and lacks of tightness therebetween, the seat would be pulled out of the valve apparatus to damage the valve apparatus.